Electrochemical gas sensors are generally known. They are typically used to detect various chemical components of gas mixtures.
The electrolyte used in the sensor is an essential component of such an electrochemical sensor. The electrolyte is in conductive contact with at least one anode and one cathode (electrodes). If the gas to be detected enters into the electrochemical sensor, a reaction typically takes place between the gas, the electrolyte and the material of the electrodes (electrode material). This reaction leads to a measurable current flow between the anode and the cathode of the sensor. This reaction takes place in electrochemical gas sensors at a so-called three-phase boundary, which is formed at the respective electrode (anode and/or cathode) from a solid phase, a liquid phase and a gaseous phase. The solid phase is typically the material of the electrode. The liquid phase is formed by the usually aqueous electrolyte. The gaseous phase is the gas mixture to be analyzed.
For example, DE 10 2005 020 719 B3 proposes in this connection an electrochemical gas sensor in which the electrodes are wetted with an electrolyte layer. The electrode surface is covered here with the electrolyte extensively but not completely. It is important in this connection that the respective electrode is neither flooded completely by electrolyte, nor does it dry out completely. However, in addition to the difficult manufacturability of such a system, a relatively high susceptibility to fluctuations in the humidity of the air also often arises as a problem in this connection. For example, relatively high humidity of the air may thus lead to an increase in the electrolyte layer thickness. This may even lead to a change in the conductivity of the electrolyte, for example, due to the absorption of water. Such a change in the conductivity is infrequently accompanied by a fluctuation in the measurement performance. The three-phase boundary necessary for the reaction may also increase or decrease now, which in turn may be associated fluctuations in the sensitivity of the sensor.
Wick systems, which make it possible to transport and store the electrolyte, are frequently used to avoid this. Excess electrolyte on the electrode surfaces can be removed here from the electrodes through the pore system of the wick. Conversely, additional electrolyte can be made available from the wick system in case of an electrolyte deficiency for the formation of an optimal three-phase boundary.
However, another problem is in this connection that the absorption of the electrolyte may be greatly inhibited by the frequently hydrophobic properties of the electrode surfaces or even of the wick material. The measurement properties of such a system are possibly greatly limited in certain areas of the surrounding area. The wetting of electrode surfaces plays a role in other technical fields as well. Thus, to improve the wetting of electrode surfaces in tetraethylammonium batteries, U.S. Pat. No. 6,280,883 B1 proposes the use of an electrolyte composition that contains a conductive salt, on the one hand, and a compound called surfactant salt, on the other hand. However, the goal is to cover the electrodes with electrolyte as rapidly and completely as possible during the manufacture.